RSVP Interface-Based Receiver Proxy

The RSVP Interface-Based Receiver Proxy feature lets you configure a proxy router by outbound interface instead of configuring a destination address for each flow going through the same interface.

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Feature Overview of RSVP Interface-Based Receiver Proxy

The RSVP Interface-Based Receiver Proxy feature allows you to use RSVP to signal reservations and guarantee bandwidth on behalf of a receiver that does not support RSVP, by terminating the PATH message and generating a RESV message in the upstream direction on an RSVP-capable router on the path to the endpoint. An example is a video-on-demand flow from a video server to a set-top box, which is a computer that acts as a receiver and decodes the incoming video signal from the video server.

Because set-top boxes may not support RSVP natively, you cannot configure end-to-end RSVP reservations between a video server and a set-top box. Instead, you can enable the RSVP interface-based receiver proxy on the router that is closest to that set-top box.

The router terminates the end-to-end sessions for many set-top boxes and performs admission control on the outbound (or egress) interface of the PATH message, where the receiver proxy is configured, as a proxy for Call Admission Control (CAC) on the router-to-set-top link. The RSVP interface-based receiver proxy determines which PATH messages to terminate by looking at the outbound interface to be used by the traffic flow.

You can configure an RSVP interface-based receiver proxy to terminate PATH messages going out a specified interface with a specific action (reply with RESV, or reject). The most common application is to configure the receiver proxy on the edge of an administrative domain on interdomain interfaces. The router then terminates PATH messages going out the administrative domain while still permitting PATH messages transitioning through the router within the same administrative domain to continue downstream.

In the video-on-demand example described above, the last-hop Layer 3 router supporting RSVP implements the receiver proxy, which is then configured on the interfaces facing the Layer 2 distribution network (for example, Digital Subscriber Line access [DSLAM] or cable distribution). Also, since RSVP is running and performing CAC on the router with the receiver proxy, you can configure RSVP enhancements such as local policy and Common Open Policy Service (COPS) for more fine-grained control on video flow CAC.

The router terminates the end-to-end sessions for many set-top boxes, with the assumption that the links further downstream (for example, from the DSLAM to the set-top box) never become congested or, more likely, in the case of congestion, that the voice and video traffic from the router gets the highest priority and access to the bandwidth.

Benefits of RSVP Interface-Based Receiver Proxy

Ease of Use and Scalability Improvement

Previously, you had to configure a receiver proxy for every separate RSVP stream or set-top box. Now you can configure the proxy by outbound interface. For example, if there were 100 set-top boxes downstream from the proxy router, you had to configure 100 proxies. With this enhancement, you configure only the outbound interface(s). In addition, the receiver proxy is guaranteed to terminate the reservation only on the last hop within the core network. Nodes that may function as transit nodes for some PATH messages but should proxy others depending on their placement in the network can perform the correct functions on a flow-by-flow basis.

In the video-on-demand example described above, a PATH message that transits through an edge router to another edge router (around the edge) is not terminated, whereas an otherwise identical PATH message that actually exits the aggregation network and transitions to the access network is terminated. This allows for more accurate CAC in the network and also simplifies and reduces configuration requirements.

Configuring a Receiver Proxy (Listener) on a Middle Router on Behalf of Tailend Routers

The following example configures a receiver proxy, also called a listener, on the middle router (Router 2) on behalf of the two tailend routers (Routers 3 and 4):

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# interface ethernet 2/0

Router(config-if)# ip rsvp listener outbound reply

Router(config-if)# exit

Router(config)# interface ethernet 3/0

Router(config-if)# ip rsvp listener outbound reject

Router(config-if)# end

Configuring PATH Messages from a Headend Router to Tailend Routers to Test the Receiver Proxy

Note If you do not have another headend router generating RSVP PATH messages available, configure one in the network for the specific purpose of testing RSVP features such as the receiver proxy. Note that these commands are not expected (or supported) in a final deployment.

The following example configures four PATH messages from the headend router (Router 1) to the tailend routers (Routers 3 and 4):

The following example verifies that the PATH messages you configured are in the database:

Router# show ip rsvp sender

To From Pro DPort Sport Prev Hop I/F BPS

10.0.0.5 10.0.0.1 TCP 2 2 none none 100K

10.0.0.5 10.0.0.1 UDP 1 1 none none 100K

10.0.0.7 10.0.0.1 TCP 4 4 none none 100K

10.0.0.7 10.0.0.1 UDP 3 3 none none 100K

The following example verifies that a PATH message has been terminated by a receiver proxy configured to reply.

Note A receiver proxy that is configured to reject does not cause any state to be stored in the RSVP database; therefore, this show command does not display these PATHS. Only one PATH message is shown.

RFCs

RFC

Title

RFC 2205

Resource ReSerVation Protocol (RSVP)

Technical Assistance

Description

Link

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Command Reference

ip rsvp listener outbound

To configure a Resource Reservation Protocol (RSVP) router to listen for PATH messages sent through a specified interface, use the ip rsvp listeneroutbound command in interface configuration mode. To disable listening, use the no form of this command.

ip rsvp listener outbound {reply|reject}

no ip rsvp listener outbound {reply|reject}

Syntax Description

reply

For a PATH message that usually exits from a specified interface, the router does the following:

•Installs local PATH state for the message.

•Terminates the PATH message and does not forward it downstream.

•Generates and sends a RESV (reply) message upstream on behalf of the PATH message with the following.

–The objects in the RESV message are the same as those in the PATH message.

–The policy objects, such as preemption and application IDs, are echoed back.

–Shared explicit style is used.

reject

For a PATH message that usually exits from a specified interface, the router does the following:

•Terminates the PATH message and does not forward it downstream.

•Generates and sends a PATHERROR (reject) message upstream.

•Does not install local PATH state and discards the PATH message.

Command Default

This command is disabled by default; therefore, no listeners are configured.

Command Modes

Interface configuration

Command History

Release

Modification

12.2(18)SFX5

This command was introduced.

12.2(33)SRB

This command was integrated into Cisco IOS Release 12.2(33)SRB.

Usage Guidelines

Use the ip rsvp listener outbound command to match all PATH messages that are being sent from a specified interface.

When you configure an interface-based receiver proxy to reply, RSVP performs Call Admission Control (CAC) on the outbound (or egress) interface for the flow. If CAC fails, the reservation is not generated. This is the same behavior as for the global RSVP receiver proxy command.

The outbound interface that a flow uses is determined when the flow is set up, and the interface-based receiver proxy is consulted at that time. The interface-based receiver proxy is not consulted if there is a change in routing for an existing flow.

If the interface-based receiver proxy receives a RESVERR message with an admission control failure error or a policy reject error, the interface-based receiver proxy generates a PATHERR message with the same error to provide explicit notification to the sender of the reservation failure.

Examples

In the following example, PATH messages sent through Ethernet interface 3/0 are rejected and PATHERROR messages are generated:

Feature Information for RSVP Interface-Based Receiver Proxy

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

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Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Table 1 Feature Information for RSVP Interface-Based Receiver Proxy

Feature Name

Releases

Feature Information

RSVP Interface-Based Receiver Proxy

12.2(28)SXF5 12.2(33)SRB

The RSVP Interface-Based Receiver Proxy feature lets you configure a proxy router by outbound interface instead of configuring a destination address for each flow going through the same interface.

In Cisco IOS Release 12.2(33)SRB, support was added for the Cisco 7600 series routers.

Glossary

flow—A stream of data traveling between two endpoints across a network (for example, from one LAN station to another). Multiple flows can be transmitted on a single circuit.

PE router—provider edge router. A router that is part of a service provider's network and is connected to a customer edge (CE) router.

proxy—A component of RSVP that manages all locally originated and terminated state.

receiver proxy—A configurable feature that allows a router to proxy RSVP RESV messages for local or remote destinations.

RSVP—Resource Reservation Protocol. A protocol for reserving network resources to provide quality of service guarantees to application flows.

set-top box—A computer that acts as a receiver and decodes the incoming signal from a satellite dish, a cable network, or a telephone line.

Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.